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Animals have life cycles with a single diploid multicellular phase that produces haploid gametes directly by meiosis. Male gametes are called sperm, and female gametes are called eggs or ova. In animals, fertilization of the ovum by a sperm results in the formation of a diploid zygote that develops by repeated mitotic divisions into a diploid ...
This is an accepted version of this page This is the latest accepted revision, reviewed on 5 January 2025. Cell division producing haploid gametes For the figure of speech, see Meiosis (figure of speech). For the process whereby cell nuclei divide to produce two copies of themselves, see Mitosis. For excessive constriction of the pupils, see Miosis. For the parasitic infestation, see Myiasis ...
This is an accepted version of this page This is the latest accepted revision, reviewed on 6 January 2025. Procreative biological processes of humanity Part of a series on Sex Biological terms Sexual dimorphism Sexual differentiation Feminization Virilization Sex-determination system XY XO ZW ZO Temperature-dependent Haplodiploidy Heterogametic sex Homogametic sex Sex chromosome X chromosome Y ...
In both males and females, the sex organs consist of two structures: the internal genitalia and the external genitalia. In males, the gonads are the testicles and in females, they are the ovaries . These are the organs that produce gametes (egg and sperm), the reproductive cells that will eventually meet to form the fertilized egg ( zygote ).
Meiosis generates genetic variation in the diploid cell, in part by the exchange of genetic information between the pairs of chromosomes after they align (recombination). Thus, on this view, [28] an advantage of meiosis is that it facilitates the generation of genomic diversity among progeny, allowing adaptation to adverse changes in the ...
Females can produce full clones of themselves through a modification of the normal meiosis process used to produce haploid egg cells for sexual reproduction. The female's germ cells undergo a process of premeiotic genome doubling, or endoreduplication, so that two consecutive division cycles in the process of meiosis result in a diploid, rather than haploid, genome.
When YY males mate with XX females, all their progeny would be XY male if grown under normal conditions. [ 69 ] Support for the hypothesis is found in the common frog , for which XX males and XY males both suppresses sex chromosome recombination, but XX and XY females both recombine at the same rate.
The model organism Caenorhabditis elegans—a nematode frequently used in biological research—is one such organism. Most spiders have a variation of the XO system in which males have two different X chromosomes (X 1 X 2 O), while females have a pair of X 1 chromosomes and a pair of X 2 chromosomes (X 1 X 1 X 2 X 2). [1]